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Comment by cowardlydragon | Hacker News Reader

... aaand meanwhile we continue to ignore LFTR / Thorium as a present-day practical, demonstrated in the 1960s scalable super safe non-proliferation nuclear energy option that seems to be held up by bureaucracy or lack of patentability.

And from what I've read, don't the fusion reactors also become radioactive from the high energy neutrons in fusion reactors? Yes the fuel isn't radioactive... but they also need to be scrapped/reprocessed after (pulling number out of butt) five years?

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You are right in saying that Thorium reactors are receiving too little attention. However due to their breeder nature they also produce nuclear waste which needs to be stored for hundreds of years. The main advantage of fusion is that you only get light radioactive istotopes of Helium or Lithium which decay within hours or days. The reactor walls are activated through neutron capture, which renders these highly radioactive for 50 to 100 years [1]. In comparison to fission reactors, that's not very long.

[1] https://en.wikipedia.org/wiki/Fusion_power#Waste_management

The idea of Thorium reactors as a better nuclear fuel option, gets proposed frequently on HN. There are real issues with it though. There are reasons why it is not a fuel of choice today, that have nothing to do with conspiracy theories. A small amount of searching will reveal this.

You may be right, but without references this is just a content-free sneer.

10 seconds on a search engine will supply 1000's of links to issues with Thorium and LFTR, some of which are high quality and some of which are garbage. Note that the OP did not provide links in support of their position.

You have a chance to add more to conversation than the OP, then. For myself, I'd be very interested in two or three relevant links, if you can provide them.

Thorium molten salt reactors need an attached chemical reprocessing plant which runs on radioactive fluoride fuel salts. Chemical processing plants for radioactive materials are a huge headache. Most of the older ones are now Superfund toxic sites.

The great thing about pressurized-water reactors and boiling water reactors is that they work on water, which is easy to handle and doesn't itself become highly radioactive. The radioactive portions of commercial nuclear reactors are very simple, with very few moving parts. The complexity is outside the reactor vessel.

Most of the alternative reactor designs have much more complex radioactive portions. Pebble bed reactors get pebble jams. (An experimental pebble-bed reactor in Germany has been jammed for decades, and still can't be decommissioned.) Helium-cooled reactors leak. (Ft. St. Vrain was so promising.) Sodium cooled reactors have sodium fires.

That's why alternative nuclear technologies haven't caught on. If you need 40 years of trouble-free operation to make a plant pay, none of those technologies qualify.

LFTR's are very safe, but the current technical challenge is actually building containments that can handle heat + flouride salts. The tritium formed during the nuclear reactions is also challenging to handle, as it passes through those walls via diffusion. Until we find materials that can cope with these situations, it will remain a dream. Advances in nanotechnology will bring us further here, I totally agree with you though that LFTR's by far get too little attention, as today's nanotechnology could solve it for us.

The waste coming out of LFTR's has to be stored ~400 years (which is actually a sane timespan and it's easy to find places underground that stay stable for 400 years). Another bonus is the fact that Thorium is much easier to find than Uranium, and that an LFTR can be built more or less failsafe.

Yes, neutron activation is a source of radioactivity, but the results are short-lived (~10 yrs) radioactive isotopes. The problem with fission waste isn't necessarily the quantity of radiation, but the fact that the timescales are far beyond what humanity can count on.

That said, I'm convinced we'll have to deal with it. Fusion will be ready when the uranium runs out.

>...The problem with fission waste isn't necessarily the quantity of radiation, but the fact that the timescales are far beyond what humanity can count on.

Nuclear waste can and should be recycled which would reduce the amount of waste. https://en.wikipedia.org/wiki/Radioactive_waste

Eventually it will be possible to use most of the waste as fuel http://en.wikipedia.org/wiki/Integral_fast_reactor

>...That said, I'm convinced we'll have to deal with it. Fusion will be ready when the uranium runs out.

With breeder reactors, we could run the world on nuclear power and have enough fuel for tens of thousands of years. By then I would hope fusion would be ready.

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